Coastal Zone Color Scanner (CZCS)

Description

The Coastal Zone Color Scanner Experiment (CZCS) was designed to map chlorophyll concentration in water, sediment distribution, gelbstoffe concentrations as a salinity indicator, and temperature of coastal waters and ocean currents. Reflected solar energy was measured in six channels to sense color caused by absorption due to chlorophyll, sediments, and gelbstoffe in coastal waters. The CZCS was a multi-channel scanning radiometer which used a rotating plane mirror at a 45 degree angle to the optic axis of a Cassegran telescope. The mirror scanned 360 degrees but only the 80 degrees of data centered on nadir were collected for ocean color measurements. The instrument viewed deep space and calibration sources during the remainder of the scan. The incoming radiation was collected by the telescope and divided into two streams by a dichroic beam splitter. One stream was transmitted to a field stop that was also the entrance aperature of a small polychromator. The radiance that entered the polychromator was separated and re-imaged in five wavelengths on five silicon detectors in the focal plane of the polychromator. The other stream was directed to a cooled mercury cadmium telluride detector in the thermal region (10.5-12.5 micrometer). A radiative cooler was used to cool the thermal detector. To avoid sun glint, the scanner mirror was tilted about the sensor pitch axis on command so that the line of sight of the sensor was moved in 2-deg increments up to 20 deg with respect to the nadir. Spectral bands at 0.443 and 0.670 micrometers centered on the most intense absorption bands of chlorophyll, while the band at 0.550 micrometers centered on the "hinge point," the wavelength of minimum absorption. Ratios of measured energies in these channels were shown to closely parallel surface chlorophyll concentrations. Data from the scanning radiometer were processed, with algorithms developed from the field experiment data, to produce maps of chlorophyll absorption. The temperatures of coastal waters and ocean currents were measured in a spectral band centered at 11.5 micrometers. Observations were made also in two other spectral bands, 0.520 micrometers for chlorophyll correlation and 0.750 micrometers for surface vegetation. The scan width was 1556 km centered on nadir and the ground resolution was 0.825 km at nadir. For a more detailed description, see Section 2 in "The Nimbus 7 Users' Guide" (TRF B30045), available from NSSDC. Data are archived at SDSD. Since mid-1984, the instrument experienced occasional start-up problems. It was finally turned off in December 1986.